By Sid Perkins
Scientists seeking to cool Earth’s climate by injecting millions of tons of sulfuric acid droplets high in the atmosphere might trim rising temperatures but could also destroy much of the ozone in polar regions, a new study suggests.
Major volcanic eruptions spew large amounts of tiny particles, or aerosols, high into the atmosphere, where they scatter light back to space and significantly cool Earth for months to years (SN: 2/18/06, p. 110). Some researchers have proposed lofting tons of aerosols into the stratosphere to achieve the same result, but that process — often dubbed geoengineering — could have a number of detrimental side effects. Last year, for example, scientists noted that average precipitation worldwide dropped significantly in the 16 months immediately following the 1991 eruption of Mount Pinatubo (SN: 8/25/07, p. 125).
Now, count ozone destruction among the drawbacks of geoengineering. High-altitude ozone helps block damaging ultraviolet radiation from reaching Earth’s surface. Ozone-destroying chemical reactions occur most readily on the surfaces of high-altitude ice crystals and droplets of sulfuric acid spewed by volcanoes, says Simone Tilmes, an atmospheric scientist at the NationalCenter for Atmospheric Research in Boulder, Colo.
So, Tilmes and her colleagues estimated the ozone loss that would be triggered by two geoengineering scenarios, each designed to counteract the warming effect caused by doubling the pre-industrial atmospheric levels of carbon dioxide, as expected to occur late this century.